Method of transmitting messages by means of ultra short waves



Sept. 21, 1937.

D. PRINZ METHOD OF TRANSMITTING MESSAGES BY MEANS OF ULTRA SHORT WAVES Filed Feb. 15, 1955 DiETR INYENTOR. ICH PRWZ ATTORNEY.

2O ments in the position of the transmitter elements Patented Sept. 21 1937 UNlTED STATES PATENT @FHQE METHOD OF TRANSMITTING MESSAGES BY MEANS OF ULTRA SHORT WAVES Dietrich Prinz, Berlin, Germany, assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic m. b. H., Berlin, Germany, a corporation of Germany Application February 15, 1935, Serial No. 6,680 In Germany February 21, 1934 2 Claims.

The invention relates to a circuit for operating ultra-short wave transmitters and which circuit affords a selective reception.

As is known, an amplification of ultra-short 5 waves was hitherto not practically possible. Hence it is necessary to have the first tube in the receiver operating as a demodulator, and to further amplify the signals only after they have been obtained by the demodulation. Since a series connection of numerous audio frequency waves However, considerable difiiculties are hereby encountered. The cause thereof lies in the hitherto still insufficient constancy of the ultra-short wave producers, since slight variations in the operating voltage as well as displacewhich determine the frequency are capable of causing appreciable wave fluctuations.

superposed by an oscillation whose frequency.

deviates from that of the incoming wave, and in which the beat frequency is amplified. been proposed already to modulate several times It has the ultra-high frequency carrier oscillation in first modulating the transmitter by a long wave intermediate frequency whose wave. length is for instance several 100 meters, and to then impress upon this auxiliary carrier the signal frequency. This method also does not give completely satisfactory results.

In general, the selectivity of the input circuit tuned to the ultra-high frequency is entirely insufficient for separating various transmitters which are close to each other in the frequency band, and this is the more true since in most cases only a single resonance circuit tuned to the carrier frequency is available.

additional difficulty resides in the fact that the individual transmitters, due to their inconstancy, deviate from their assigned waves thus disturbing each other.

In accordance with the invention, the selectivity at the receiver side is essentially improved by utilizing for the intermediate modulation of the ultra-short wave transmitter an auxiliary frequency derived from a frequency stabilizing generator.

Known means can be used for the control of the intermediate frequency generator, such as slightly damped resonance lines, piezoelectric crystals, bars excited by means of mag neto-striction, etc. In using these stabilizing means it is possible to apply, in the intermediate frequency part of the. receiver, such a sharp selection that a distinct separation of various transmitters is rendered possible, despite eventual fluctuation of the ultra-high frequency carrier Wave, or despite an insufficiency in the selection of the input circuit tuned to the high frequency. The further possibility exists in operating various transmitters with exactly or approximately exactly the same high frequency carrier wave, and with different accurately stabilized intermediate frequencies. The selectivity of the intermediate frequency part of the receiver can be increased to a high value in a manner known as such, for instance by the use of especially sensitive resonators (for instance piezo-electric crystals).

It should be especially noted that the subject matter of the present application makes it possible for the first time to use, in the range of ultra-short waves, such a great number of transmitters without mutual disturbance, as the scope of this frequency band permits, in view of the side bands produced by the modulation of the signal carrier waves. In this manner an essentially more intensive exploitation of the ultrashort wave band is thus obtained than would be possible by the use of ultra-high frequency resonance circuits. This cannot be accomplished unless the individual intermediate frequencies are stabilized, since it is then possible to apply such a high selectivity in the intermediate frequency receiver.

The application of the method in accordance with the invention appears to be the more suited since the range of variation of the wave of ultra.- short Wave receivers is in general relatively small, which entails the problem of providing a greater number of transmitting stations within a comparatively narrow frequency band.

The principal arrangement of a transmitter installation operating in accordance with the present invention is schematically represented in the drawing.

In the drawing, S is, for instance, a tube operating in a braking field circuit, and in which an ultra-high frequency carrier oscillation is produced, and applied to the dipole antenna A across a tuned parallel wire system L, and radiated from the said antenna. The braking field circuit, it will be appreciated, employs the phenomena of pendulum motion of electrons about a grid of a tube to which a high positive potential is applied, while to the plate of the tube a much lower potential, such as a slightly negative potential, is applied. The auxiliary carrier oscillation is produced in a stage H stabilized by means of the piezo-electric quartz crystal Q, and said oscillation will be modulated by audio frequency voltages supplied by a microphone M, this modulation taking place in a subsequent stage V. The modulation of the main transmitter tube S takes place, for instance, due to influencing the braking electrode by means of a coupling coil K inserted in the braking current circuit. The choke coils D prevent the ultrahigh frequency from leaking into the operating voltage source, in a known manner.

In the present example, a circuit has been described in which the intermediate frequency as well as the ultra-short wave is modulated in amplitude. Obviously, without departing from the spirit of the invention, other modulation methods known as such can also be utilized.

What is claimed is:

1. An ultra short wave transmitter having, in combination, a first oscillator tube generating ultra-high frequencies, and a second stabilized oscillator tube generating lower frequencies, said first tube having anode, cathode and grid electrodes, energy means for supplying a high positive potential to said grid and a much lower potential to said anode relative tosaid cathode, a modulator tube having input and output circuits, an inductive connection including series connected choke coils for coupling the anode and grid of said first oscillator to the output of said modulator, means for inductively coupling said second oscillator to the input of said modulator, a Lecher wire system directly connected at one end to said anode and grid, and an antenna directly'connected to the other end of said Lecher Wire system.

2. A transmitter in accordance with claim 1, including a microphone coupled to the input of said modulator and characterized in this, that said second oscillator tube is stabilized by means of a piezo-electric crystal, and said antenna comprises a doublet, there being also provided a tunable condenser connected across said Lecher wires.

DIETRICH PRINZ. 

